The measurement of the distance or length of route travelled (covered) by a vehicle is one of the bases of toll calculation in modern road toll systems that are based on digital map material. For this purpose, vehicle positions (“position fixes”) determined by satellite navigation, for example, are matched to the road segments of the digital road map by “map matching” and the distance travelled is determined from the lengths thereof. However, this procedure is subject to a significant amount of inaccuracy, since it is based on idealised assumptions: the road segments of currently available digital road maps represent real roads in an idealised linear form for the purpose of simplifying and reducing the storage requirements. In this case, the segment lengths of the road segments are respectively defined between the intersection mid-points of the real roads.